Blueprint Medicines stock was soaring Monday after French drugmaker Sanofi said it had agreed to buy the biotech company for $9.5 billion. Shares in Blueprint jumped 27% to $128.611 ahead of the opening bell.

French drugmaker Sanofi said Monday it has agreed to acquire Blueprint Medicines for $9.5 billion, sending shares of the Cambridge, Mass.-based biopharma firm soaring in premarket trading.

Sanofi has agreed to acquire US-based Blueprint Medicines for an equity value of $9.1bn to bolster its immunology pipeline with rare disease treatments. The acquisition includes Ayvakit/Ayvakyt (avapritinib),